Substantial areas of the North Burbank Unit, Osage County, Oklahoma, gave poorer than average response to waterflooding. After studies showed that the performance of these areas could be traced to greater than field average heterogeneity, a pilot polymerflood was conducted during the period from 1970-1979. Good response to polymerflooding, followed by economic evaluation of proposed expanded operations, led to the design and implementation of a 1440 acre commercial scale project.
The project involved injection of fresh water preflush during the period from September, 1980 to late April, 1981. Then a liquid emulsion type polyacrylamide was blended to 500 ppm in fresh water and injected at a total rate of 63,000 BPD until approximately 4.4 percent of the pore volume had been injected. This was followed by a water spacer, and a 0.8 percent (PV) slug of aluminum citrate containing 500 ppm of aluminum was injected as a cross-linking agent into those two-thirds of the injectors which were expected to present no injectivity problems. Following injection of a second water spacer, 500 ppm polymer injection was resumed.
Plans call for injection of polymer at 500 ppm until the total amount reaches 15 percent of pore volume. This will be followed by polymer slugs of 250 ppm (10 percent of pore volume) and 50 ppm (15 percent of pore volume), fresh water (20 percent of pore volume), and finally drive (produced) water. Any localized channeling problems will be handled by treating individual injection wells with crosslinking agents such as aluminum citrate.
Methods of scaling up pilot results to the 1440- acre commercial project, site selection, design of the fresh water preflush, estimation of aluminum citrate requirements, and project costs are discussed.